As is well known in the FLM literature, we will need some sort of regularization method to define an “approximate inverse” to \(\Gamma _n\) . We will again follow the setup of [1]} and [2]} and define the sequence \(\delta _j\) 's, \(j = 1, 2, \ldots \)  of the smallest difference between distinct eigenvalues of \(\Gamma \)  as,
\(\delta _1 &:= \lambda _1 - \lambda _2, \\\delta _j &:= \min \lbrace  \lambda _j - \lambda _{j+1}, \lambda _{j - 1} - \lambda _j \rbrace .\) 
